Jet boat nozzle



Nov. 2, 1965 l R. L. COCHRAN JET BOAT NOZZLE Filed March 14, 1963 RESERVOIR INVENTOR.

RlcHARD L. COCHRAN BY fm ZUM Sri-AMM A{'IIOYHP\ S United States Patent O 3,214,903 JET BOAT NOZZLE Richard L. Cochran, Littleton, Coin., assigner to The Buehler Corporation, Indianapolis, Ind., a corporation of Indiana Filed Mar. 14, 1963, Ser. No. 265,136 1 Claim. (Cl. 60-35.S)

The present invention relates to jet propelled watercraft.

One form of jet propelled boat incorporates an engine operatively connected to a pump located within a conduit extending through the boat from an intake opening at the bottom of the boat to an exhaust at the rear of the boat. Water is drawn into the conduit through the intake opening and is exhausted in a jet stream from the rear of the boat causing the boat to move. It has been found that the relative velocity of the jet stream as compared to the velocity of the boat has a controlling eiiect on the propulsive eiciency of the boat.

Consequently, one object of the invention is to provide -a jet boat nozzle arrangement which can be operated to propel the boat at relatively high propulsive eiciency.

A further object of the present invention is to provide an engine-powered jet-watercraft nozzle arrangement which can be controlled to cause the jet craft to operate at a relatively high miles per gallon of fuel.

Still another object of the invention is to provide an improved control system and nozzle arrangement for a jetcraft.

Related objects and advantages will become apparent as the description proceeds.

One embodiment of the present invention includes a control system for a jet-craft comprising a conduit mounted on the craft and extending and opening rearwardly thereof, means for pumping water through the conduit to exhaust from said opening. Mounted within the opening is an annular inflatable exible tube to which is connected a compressed-air-providing means. The size of the tube and the size of the opening are controlled by inating or deating the t-ube so as to control the velocity of the jet as it leaves the conduit and to thereby maintain the velocity of the jet at a desired value relatively lclose to the velocity of the boat.

The full nature of the invention will be understood from the accompanying drawings and the following description and claim.

FIG. l is a side elevation of a jet boat incorporating the novel control system of the present invention.

FIG. 2 is an enlarged side elevation of the rear portion of the jet boat of FIG. 1 with a portion broken away to show internal details of a nozzle arrangement Iforming a part of the present arrangement.

FIG. 3 is an enlarged axial section through the opening or exhaust of the pump conduit showing details of the nozzle arrangement of the present invention, said FIG. 3 also including a schematic flow diagram showing means for controlling compressed air supplied to the nozzle arrangement.

FIG. 4 is a graph showing the relationship of ideal propulsion eiciency to the velocity ratio, i.e. the jet velocity over the boat velocity.

Referring now more particularly to the drawings, there is illustrated a jet boat having a hull 11, the hull being provided with an intake opening 12 communicating Ibetween the bottom of the boat and a pump 13. The pump 13 has a passage therethrough communicating between the intake 12 and a passage 14 through a tailpipe 16 secured to the rear or transom 17 of the boat. The pump 13 is driven by a conventional marine engine 18 by means of a shaft 20 and functions to pump water from intake 3,214,903 Patented Nov. 2, 1965 12 to and out of the rear of the boat. The water is constricted into a stream by the converging surface 21 of a nozzle arrangement 22 .mounted within the exit end of the tailpipe 16.

The jet, after being formed by the nozzle arrangement 22, passes through a housing 25 secured to the rear of the boat and passes between a pair of detlectors 26 pivotally mounted on the housing. Since the Ihousing 25 and deectors 26 form no part of the present invention, they will not be further described herein. IFor further details regarding the suitable housing I25 and detiectors 26, reference is made to the copending application of James W. Reynolds et al., Serial No. 23 6,292, entitled I et Boat Steering Deectors and assigned to the same assignee as the present application.

In order to move the boat 10, it is necessary that the pump 13 changes a certain mass of water per second from one velocity to another velocity. Thus, the propulsive force or thrust developed is equal to the mass rate of ow through the system times the velocity change across the system. Or:

T=mAv where:

T=thrust in pounds mzmass of water in slugs! second Av=change in velocity of the water from its entry into the lboat to its exit out of the boat.

where T=thrust in pounds VB=velocity of the boat in ft. per second The overall system propulsive eticiency may be expressed as follows:

H P. output TVB ifm-(T) HP' mp The system eiiciency may be expressed as the product of the ideal propulsive efficiency and the mechanical efciency. Thus:

17p', the ideal propulsive eiciency represents the maximum elhciency possible in any propulsive system. As set forth above, in order to produce a thrust, there must be a change in velocity of the water pumped. It is also true, however, that the velocity change of the water pumped represents a loss of kinetic energy to the system. If the change in velocity is great, the loss of kinetic energy is even greater and in fact, is magnified as the square of the change in velocity because of the fact that kinetic energy is proportional to the square of the velocity times the mass involved.

When used for hydraulic jets, the ideal propulsive efficiency may be written:

This relation has been plotted graphically in FIG. 4.

Consequently, it is desirable that the boat be operated as r.far to the left on this graph as possible. For example, a velocity ratio of 1.5 to 1.7 provides a good balance between reducing loss of kinetic energy and high thrust. As can be read from FIG. 4, the propulsive eciency for such a velocity ratio is approximately 75%.

Assume now that the boat is moving at a given velocity which .produces the desired Velocity ratio of 1.5 to 1.7 and which produces the desired propulsive eiliciency of 75 Assume further that the boat now takes on a heavy load which appreciably reduces the boat velocity. As a result, the Velocity ratio increases `and causes the propulsive eiciency to be substantially reduced. The nozzle arrangement 22 is used to bring the jet velocity down to a figure which produces the desired velocity of 1.5 to 1.7. Thus, the jet velocity is decreased by increasing the size of the orifice 21 through the nozzle arrangement 22. As a result, a greater mass of water is pumped through the nozzle arrangement but this greater mass of Water leaves the boat in a jet having a lower velocity. In the situation that the boat 10 is carrying a heavy load which is removed from the boat, the orifice size of the nozzle arrangement 22 is reduced in order to bring the jet Velocity up to a sufficiently high value so that the boat can operate at a high speed. In order to operate the boat at a high speed, thrust must be provided and this thrust is, of course, dependent upon the change in velocity of the Water as produced by the pump.

' The nozzle arrangement 22 includes an annular infiatable flexible tube 27 of triangular cross-section which is received within and bonded to a receptacle 30. The receptacle has a generally cylindrical shape with inwardly projecting flanges 31 and 32 at the opposite ends thereof. Preferably, the outer wall of the tube 27 is bonded to the receptacle 31 whereby a certain amount of desired rigidity is provided in the mounting of the tube. The receptacle is received within a recess 35 which extends into the tailpipe 16 of the conduit yfrom the rear 36 thereof. The receptacle 30 is retained in position by a snap ring 37 which is received in a peri-pheral recess 40 opening into the recess 35 of the tail- 1 Pli should be pointed out that the inflatable tube 27 has an inner Wall 41 which tapers smoothly from a larger inside diameter at its forward end 42 to a smaller inside diameter at its rearward end 45 adjacent the exit of the tailpipe. The third side or wall of the tube is located at the rearward end of the receptacle 30 adjacent the exist of the tailpipe. Thus, the wall 41 forms an extension of the converging inside surface 46 of the tailpipe and defines an orifice which forms the jet stream. The tailpipe 16, receptacle 30 and tube 27 have aligned apertures 47, 48 and 49 therethrough which form a passage for conducting or removing compressed air from the tube 27. The tailpipe 16 has a threaded counterbore 510 which can receive a suitable air conduit indicated schematically by the dotted line 51. This conduit is controlled by a valve 52 and leads to compressed-air-supplying means including the pump 55 and a reservoir 56 which are mounted in suitable locations in the boat 10. The compressed-air-supplying means can also include a pressure control (not shown) for operating the pump when the pressure in the reservoir falls below a given value and shutting off the pump when the pressure in the reservoir rises above a given value. The valve 52 is of conventional type and can be moved to a position wherein the passage 49 and pump communicate or a position wherein the passage 49 communicates with atmosphere or a position wherein the passage 49 is closed off and the air contents of the tube 27 are maintained constant. By means of the valve, pump and reservoir, the tube 27 can be inflated to various positions, one of which is when the compressed air is removed from the tube.

illustrated in dotted lines in FIG. 3. It will be noted that when the tube 27 is inilated, a smoothly curved shape 60 results, this shape having a larger inside forward diameter in the area 61 as compared to the smaller inside rearward diameter in the area 62. When water is being forced through the tailpipe 16, the pressure of the water may deform the tube 27 so that it does not bulge uniformly across the inner wall 41 as illustrated in FIG. 3. In such a situation, the tube 27 will deform but will still maintain a smooth shape which does not appreciably interfere with the ilow of the water. Even so, the smooth shape defined will be an orice of smaller diameter than that produced Obviously, the size of the orifice can be varied through an infinite number of sizes two of which are represented by the solid and dotted lines of FIG. 3.

From the above description, it Will be obvious that the present invention provides an improved control system and nozzle arrangement for a jet-craft. It will also be obvious that because of the fact that etliciency can be maintained at a uniformly high value by means of the present nozzle arrangement, the miles per gallon of the jet-craft can also be maintained at a high value. It should also be evident from the above description that the control system of the present invention makes possible propelling of a jet boat at a relatively high propulsive efciency.

It should be understood that even though the means for inilating the tube 27 has been described as compressedair-supplying, various other types of inflation means can be used. For example, it may be preferable to use hydraulic fluid, water or some type of liquid in view of its incompressibility. Also, other gases or iluids besides air might be used.

While the invention has been illustrated and described 1n detail in the drawings and foregoing description, the lsame 1s to be considered as illustrative and not restrictive 1n character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come Within the spirit of the invention and the scope of the claim are also desired to be protected.

The invention claimed is: A control system for jet-propelled watercraft comprismg a tailpipe mounted on the craft extending rearwardly thereof and defining a rear opening; means for pumping Water through said tailpipe to exhaust from said opening; said tailpipe having an inside surface converging inwardly toward said opening; a generally cylindrical recess extendmgmto said tailpipe from the rear thereof; a generally .cylindrical receptacle received within said recess and havmg radially-inwardly-projecting ilanges at opposite ends thereof; an annular inilatable ilexible tube received within said receptacle, said tube having a triangular cross-section and having an inner wall, an outer Wall, and a third Wall; said outer wall being bonded to said receptacle; said inner wall tapering inwardly toward said rear opening in said tailpipe to form an extension of the inward converging surface of said tailpipe; the third Wall of said flexible tube being adjacent said rear opening; a snap-ring engaging said tailpipe and retaining said receptacle in said recess; said tailpipe, receptacle, and tube having an aligned passage therethrough; and means connected to said passage for providing compressed air to said tube; whereby the size of the passage through said tailpipe for movement of Water can be decreased for operation of the craft at increased speeds by inllating the flexible tube, the inflated tubek being expanded to a greater thickness near said rear open ing of said tailpipe and providing a smoothly curved shape which does not appreciably interfere with the ilow of Water through the tailpipe.

(References on following page) References Cited by the Examiner UNITED STATES PATENTS Paxton (S0- 35.6 James Z39-455 Hunter 60-355 Sausa 251-5 Billman 6035.6 Young 60-35.5

6 3,070,954 1/63 Basso 60-35.5 3,093,966 6/63 Englehart et a1. 11S-14 3,151,596 10/64 McMurtrey 60-35.5 X

FOREIGN PATENTS 576,223 5/59 Canada.

SAMUEL LEVINE, Primary Examiner. 

